1. Field of the Invention
The present invention relates to a coordinates measuring head unit and a coordinates measuring machine. More particularly, the invention relates to a coordinates measuring head unit which is compact, inexpensive, and capable of conducting measurements at high speeds with high precision, and facilitates in-situ measurements such as measurements carried out on machine tools or transport lines. The invention also relates to a coordinates measuring machine which incorporates the coordinates measuring head unit.
2. Description of the Related Art
Three-dimensional coordinates measuring machines (hereinafter also referred to as the CMM) are known as a measuring apparatus for measuring three-dimensional coordinates with high precision.
However, the conventional CMM, which has a typical measurement stroke as long as about 500 mm, includes a large base (surface plate) on which a target to be measured (for example, work) is placed, and a large gate-shaped or C-shaped frame for moving a measuring probe relative to the base. For example, the measuring probe may be a contact-type touch probe for generating a touch signal when being brought into contact with the target to be measured (hereafter the measuring target) or a noncontact-type optical probe for capturing the image of the measuring target. The CMM further includes a head which can move the gate-shaped or C-shaped frame relative to the base along one axis (for example, the front-to-rear direction) and which can accomplish a relative movement on the gate-shaped or C-shaped frame along another axis (for example, in the right and left direction) orthogonal to the one axis. The probe is configured to move relative to the head in the vertical direction orthogonal to the two axes. Accordingly, the conventional CMM had to be big enough to cover not the portion to be measured but the entirety of the measuring object, while maintaining the required precision over the whole range of the measurement stroke. For this reason, the conventional CMM was inevitably large in size and footprint, expensive, and thus not suitable for measurements conducted on machines or in-situ measurements.
To solve such problems, the present applicant suggested a simple CMM, which could be incorporated into fabrication lines, in Japanese Patent Application Laid-Open No. Hei 6-34356 (hereinafter referred to as Patent Document 1), and another CMM, which could be incorporated into machining centers, in Japanese Patent Application Laid-Open No. Hei 11-325869 (hereinafter referred to as Patent Document 2).